The U.S. military, stung this year for mistakenly shipping live anthrax samples, said on Thursday its labs were being investigated for possibly mishandling other organisms, including one that causes plague.

The disclosure came a week after the Army declared a moratorium on the production, handling, testing and shipment of biological agents and toxins.

The U.S. Centers for Disease Control and Prevention said in a statement that it was trying to determine whether there were problems with record keeping and quality management or whether there were unapproved shipments.

"At this time, there is nothing to suggest risk to the health of workers or the general public," the CDC said.

The Army said the latest investigation dated back to an Aug. 17 inspection at the Edgewood Chemical Biological Center in Maryland, where the CDC raised questions as to whether a strain of Yersinia pestis, the bacterium that causes plague, was fully virulent.

Pentagon spokesman Peter Cook said the sample was "not in a containment area, but in a freezer outside of (a) containment area." Testing done so far by the Army showed the sample was non-infectious, he said, although more tests were ongoing.

"That's the scientific work that's being done at this particular time determining exactly what happened there and whether or not, again, there was mislabeling," Cook said.

The Army said the CDC raised questions about labeling of other material, including derivatives of equine encephalitis viruses.

The CDC said it was investigating issues involving pathogens maintained at four Defense Department labs.

In late May, officials discovered live anthrax had been shipped to researchers in the United States and other countries, and in July the Pentagon said the error exposed major problems in how it handles the killer bacteria.

A Pentagon investigation found live anthrax spores were sent from Dugway Proving Ground in Utah to labs in 20 states and the District of Columbia, plus Japan, Britain, South Korea, Australia, Canada, Italy and Germany.

The U.S. military, stung this year for mistakenly shipping live anthrax samples, said on Thursday its labs were being investigated for possibly mishandling other organisms, including one that causes plague.